Protein & Its Role In Healthy Aging

After water our body is mostly composed of proteins. Indeed, proteins are the main component of cells and are essential to life. Proteins are often called “the building blocks of life”.

Proteins have complex structures: they are made up of many smaller units called amino acids. These are linked together in a chemical bond forming a long chain. Some of these amino acids are called ‘essential,’ meaning they are crucial for life but cannot be produced by the human body and must be gained through one’s diet.

There are many different types of proteins in the body. For example:

Muscle mass is made of protein

Collagen which provides strength and structure to tissues (e.g. cartilage)

Skin, hair and nails which are mainly composed of proteins

Hemoglobin which transports oxygen around the body

Most hormones which act as your body’s chemical messengers are also proteins

Enzymes which regulate all aspects of metabolism; they support important chemical reactions that allow you to digest food, generate energy to contract muscles, and regulate insulin production

Antibodies which play a role in your immune response

The importance of protein for good health

Proteins have many crucial functions. Did you know?

The fibers of the muscle are made mostly of two proteins: myosin and actin. These slender fibers slide along one another to create movement. When protein intake is too low, the mechanisms for movement can be affected.

Proteins, like actin and tubulin, trigger essential processes in all living cells. These include cell division, cell shape maintenance and movements, amongst others.

Protein in the diet

Proteins are a type of macronutrient, which, along with carbohydrates and lipids, are needed by the body to function normally. Protein generally makes up 10% to 15% of the body’s energy needs. Our body is not able to store amino acids like it does for carbohydrates and fats. So we need a daily intake of amino acids through protein in our diets to make new protein. Protein should be consumed evenly across the day and be part of each meal.

Protein can be found in:

Animal sources, such as meat, fish, eggs and dairy products. These contain the full range of essential amino acids

Grains, fruits, vegetables and nuts, which may lack one or more essential amino acid

Specific nutritional supplements

Aging adults’ challenge of getting enough protein

It’s common that people eat less food with age. Contributing factors can be lack of appetite, changes to smell and taste, living alone, little interest in cooking, or difficultly in eating due to teeth/gum or denture problems. Eating less or eating sub-optimally means that older adults often miss out on getting enough important macro and micronutrients, despite their need for many nutrients being higher.

Protein is a macronutrient of particular concern; several studies1, 2, 3, 4 have reported that elderly people consume less than the daily recommended amount of protein. Inadequate protein intake is closely linked to loss of muscle strength and functionality.

How much protein do older adults need on a daily basis?

The recommended Reference Nutrient Intake (RNI) for adults is 0.83g of protein per kilogram bodyweight per day5, 6, 7.

Several nutrition experts have recommended that elderly people should increase their protein intake compared to younger adults. The PROT-AGE study group formed by experts from around the world recommends a intake of 1.0g to 1.2g of protein per kilogram of body weight per day for seniors8. This means:

A 50+ year old man weighing 80 kilograms should consume 80 to 96g of protein per day (which corresponds to 280-340 g of chicken breast per day).

A 50+ year old woman weighing 60 kilograms should consume 60 to 72g of protein per day (corresponding to 210-250 g of chicken breast).

Older women in particular, should increase their protein intake to 1.0-1.2g of protein per kilogram of body weight per day9.

Not all protein is created equal

Dietary sources of protein include meats, eggs, plants and dairy products and not all of those are created equal. To assess the quality of dietary protein three criteria can be considered: protein biological value, protein efficiency ratio, and net protein utilization.

1. Biological value: based on the quantity of essential to non-essential amino acids. (Amino acids are the chemical units that constitute protein. While the human body can manufacture most amino acids on its own, it cannot synthesize certain amino acids in sufficient amounts to meet the body’s needs. Such amino acids are called “essential amino acids” because it is crucial that the body acquires them through dietary sources)
2. Protein efficiency ratio: indicating ability of a protein to support growth
3. Net protein utilization: percentage of amino acids converted to tissue protein versus the amino acids digested

Below are examples of different types of protein and their respective quality.

Quality Comparison between Protein Sources7

Type of Protein

Biological Value

Protein Efficiency Ratio

Net Protein Utilization

Whey (dairy)

104

3.2

92%

Milk protein (~80% Caseinate and ~20% whey protein)

91

3.1

82%

Casein (dairy)

77

2.5

76%

Soy Protein (plant)

74

2.1

61%

Additional sources support health benefits of protein for the elderly

People with low protein intake have higher bone and lean muscle mass loss:

The scientific community and health authorities such as the European Food Safety Authority (EFSA) agree that protein from diet has a beneficial effect on the whole lean body mass, including muscle mass6.

The European Food Safety authority also states that protein is essential for the growth and maintenance of bones. Bone mass is at its maximum between ages 25 and 35 years and after this, there is a gradual decrease, which becomes more prominent with time11.

Older adults should seek to get enough protein through a healthy and balanced diet, and/or with the support of high quality nutritional supplements.